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Message ID: 4410     Entry time: Fri Mar 18 11:29:36 2011
Author: josephb 
Type: Update 
Category: CDS 
Subject: Minute trend issues 

[Joe, Alex]

Steve pointed out to me today he couldn't get trends for his PEM slow channels like C1:PEM-count_full. 

I experimented a bit and found for long time requests (over 20 days), it would produce minute trends up to the current time, but only if they started far enough back.  So the data was being written, but something was causing a problem for dataviewer/NDS to find it.

On further investigation it looks to be some incorrect time stamps at several points in the last few months are causing the problems.  Basically when Alex and I made mistakes in the GPS time stamp settings for the frame builder (daqd) code, the wrong time got written for hours to the raw minute trend data files.

So Alex is going to be running a script to go through the roughly 180 gigabytes of affected trend data to write new files with the correct time stamps.  Once it done, we'll move the files over.  We'll probably lose a few hours worth of recent trend data, depending on how quickly the scripts run, but after which minute trends should work as they are supposed to.

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